344. Reverse String

问题简述
Write a function that reverses a string. The input string is given as an array of characters s.

You must do this by modifying the input array in-place with O(1) extra memory.

双指针，同时更新并交换两个数值。

class Solution {
    public void reverseString(char[] s) {
        int i = 0;
        int j = s.length - 1;
        
        while( i < j ) {
            char temp = s[i]; 
            s[i] = s[j];
            s[j] = temp;
            
            i++;
            j--;
        }
    }
}